1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
|
// Copyright (C) 2025 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include "queueworker.h"
/* view needs 8 items and cacheBuffer of 2 items above and below to show visible area, so limit queue max length to that. */
static constexpr int s_queueMaxLength{12};
QueueWorker::QueueWorker()
: QObject{nullptr}
{
connect(this,
&QueueWorker::triggerQueueProcessing,
this,
&QueueWorker::processQueue,
Qt::QueuedConnection);
}
void QueueWorker::abort()
{
m_killSignalReceived = true;
}
void QueueWorker::fetchData(int id)
{
if (m_indicesAlreadyFetched.contains(id) || m_indicesToFetch.contains(id)
|| m_killSignalReceived)
return;
/* This is signal from UI thread. It is likely that there are more than one in queue.
* Add our own triggerQueueProcessing() signal to the end of event queue and add id to queue of IDs.
* Then let all queued signals to be processed until QueueWorker receives its own signal.
*/
sendTriggerQueueProcessingSignal(id);
}
void QueueWorker::processQueue()
{
/* This slot receives QueueWorker's own signal after all signals from UI thread have been processed. */
m_queueProcessingSignalSent = false;
const auto index = m_indicesToFetch.dequeue();
emit processing(index);
const auto data = m_remoteMedia.getElements(1, index);
m_indicesAlreadyFetched.insert(index);
emit dataFetched(index, data.front());
if (!m_indicesToFetch.empty() && !m_killSignalReceived) {
/* Queueworker should process more indices, but the UI thread may have sent more signals during previous processing.
* Add our own signal to end of event queue and let all preceding signals to be processed before continuing.
*/
emit triggerQueueProcessing(QPrivateSignal{});
m_queueProcessingSignalSent = true;
}
/* Else all fetches have been processed so far. */
}
void QueueWorker::sendTriggerQueueProcessingSignal(int id)
{
/* Make sure excess IDs are removed. */
while (m_indicesToFetch.size() >= s_queueMaxLength) {
emit dropped(m_indicesToFetch.dequeue());
}
/* Before calling this function QueueWorker has ensured that m_indicesToFetch doesn't contain id yet, so just add id. */
m_indicesToFetch.enqueue(id);
if (!m_queueProcessingSignalSent) {
emit triggerQueueProcessing(QPrivateSignal{});
m_queueProcessingSignalSent = true;
}
}
|
